Piston customize response representation

You can return custom format by returning a Python dictionary. Here is an example on one of my app. I hope it helps.

from models import *from piston.handler import BaseHandlerfrom django.http import Http404class ZipCodeHandler(BaseHandler):    methods_allowed = ('GET',)    def read(self, request, zip_code):        try:            points = DeliveryPoint.objects.filter(zip_code=zip_code).order_by("name")            dps = []            for p in points:                name = p.name if (len(p.name)<=16) else p.name[:16]+"..."                dps.append({'name': name, 'zone': p.zone, 'price': p.price})            return {'length':len(dps), 'dps':dps}            except Exception, e:            return {'length':0, "error":e}

Its been two years since this question was asked, so its obviously late for OP. But for others who, like me, had a similar dilemma there exists a Pistonic way to get this done.

Using the Django example of polls and choices -

You will notice that for the ChoiceHandler the JSON response is:

[    {        "votes": 0,        "poll": {            "pub_date": "2011-04-23",            "question": "Do you like Icecream?",            "polling_ended": false        },        "choice": "A lot!"    }]

This includes the entire JSON for the associated poll whereas just the id for it could have been just as good if not better.

Let's say that the desired response is:

[    {        "id": 2,        "votes": 0,        "poll": 5,        "choice": "A lot!"    }]

Here's how you would edit the handler to achieve that:

from piston.handler import BaseHandlerfrom polls.models import Poll, Choiceclass ChoiceHandler( BaseHandler ):  allowed_methods = ('GET',)  model = Choice  # edit the values in fields to change what is in the response JSON  fields = ('id', 'votes', 'poll', 'choice') # Add id to response fields  # if you do not add 'id' here, the desired response will not contain it   # even if you have defined the classmethod 'id' below  # customize the response JSON for the poll field to be the id   # instead of the complete JSON for the poll object  @classmethod  def poll(cls, model):    if model.poll:      return model.poll.id    else:      return None  # define what id is in the response  # this is just for descriptive purposes,   # Piston has built-in id support which is used when you add it to 'fields'  @classmethod  def id(cls, model):    return model.id  def read( self, request, id=None ):    if id:      try:        return Choice.objects.get(id=id)      except Choice.DoesNotExist, e:        return {}    else:      return Choice.objects.all()

Django comes with a serialization library. You'll also need a json library to get it into the format you want

http://docs.djangoproject.com/en/dev/topics/serialization/

from django.core import serializersimport simplejsonclass CarHandler(AnonymousBaseHandler):    allowed_methods = ('GET',)    model = Car    fields = ('name', 'color',)    def read(self, request, car_id):           return simplejson.dumps( serializers.serialize("json", Car.get(pk=car_id) )